Wind turbine blades are normally manufactured as first and second blade shells, using a pair of adjacent blade moulds. The blade moulds comprise first and second moulding surfaces conforming to the upwind and downwind halves (or the suction and pressure sides) of a wind turbine blade, the first blade mould used to form a first blade shell and the second blade mould used to form a second blade shell, the shells subsequently joined together to form a wind turbine blade.
A fibrous composite material is initially layered on top of the first and second moulding surfaces, the layers of material conforming to the contours of the moulds to form the external aerodynamic surfaces of the blade shells. Once sufficient layers of the fibrous material have been applied in the moulds, a resin is applied to the fibrous material to cure the material, to allow it to harden. The resin is most commonly infused using a vacuum bag system, and takes approximately 2-3 hours from the start of resin infusion to a time when the blade shells are effectively cured to have a resilient structure.
Once the blade shells have sufficiently cured, the vacuum bags are removed and further operations can be performed on the hardened shells. For example, blade laminates and/or webs can be installed in the blade shells, various repair or patching operations may be carried out on the shells, grinding of shell surfaces, etc.
Next, an adhesive glue is applied to the edges of the shells while in the moulds. The blade moulds are linked via a hinged turning mechanism, and a first of the blade moulds, containing a first of the blade shells, is accordingly turned relative to the second mould and shell, such that the first shell is positioned above the second shell. This allows for the blade shells to be closed together along the edge of the shells, to form a complete wind turbine blade having an upwind and a downwind side. To allow for secure bonding of the shells together, a suitable pressure is maintained along the exterior surfaces of the blade shells by the blade moulds, usually for approximately 3-4 hours.
Once the complete wind turbine blade is fully adhered, the first blade mould may be hinged back to an open state, allowing access to the contained wind turbine blade. The blade can then be de-moulded from the second blade mould, and supported using blade carts to perform additional production operations, e.g. grinding of the external blade surface, coating, etc.
High-quality blade moulds are one of the most expensive pieces of equipment in the blade manufacturing process, requiring extensive tooling and manufacture before use to ensure accurate reproduction of desired blade profiles, as well as to allow for the turning of the moulds to bond blade shell parts together. In addition, even a minor difference in blade characteristics such as length, camber, etc. will in general require a completely new blade mould for the manufacturing process.
Blade moulds in use in current processes can cost approximately €1-3 million to manufacture and, dependent on where the moulds are made, extensive transportation time may be a factor before a new mould can be used at a manufacturing plant. This introduces considerable expense and lead time in the implementation of a manufacturing process for a new wind turbine blade.
Accordingly, one of the limitations to efficient implementation of wind turbine technology is the time required for the initial setup of a blade manufacturing system. A further limitation is the time taken for the manufacturing of individual blades within such a system.
A prior art blade manufacturing system which aims to decrease mould occupancy time is described in U.S. Patent Application Publication No. US 2011/0100533. However, the use of such a system will result in an increase in the time required to produce a single wind turbine blade, due to the increase in manufacturing operations involved.
It is an object of the invention to provide a system and a method of manufacture of a wind turbine blade which reduces these limitations.